Theoretical background of Fourier transform infrared spectroscopy (FTIR) is provided; information on sampling methods identifies the need for a method to separate the components. Comments on the various types of chromatography, such as gas, high-pressure liquid, and thin-layer, indicate the state of the art of the techniques. Similarly, advantages and disadvantages of attenuated total reflection (ATR) spectroscopy are presented; photothermal beam deflection spectroscopy (PBDS) is introduced. The analysis of the papers demonstrates how FTIR is used. Papers from the 19th century were shown to have similar degradation products; the degradation products from the foxing, similar to those from the papers, suggest that foxing may be accelerated aging catalyzed by an agent at the foxing site. Reflectance spectrometry was useful in identifying a gelatin size on the paper. Organic components that result from the method or the solvents used in the analysis may show up in the data these need to be interpreted accordingly. -- AATA